Lemon Bar Sheet Cake (Print Version)

A decadent dessert blending zesty lemon cake with shortbread crust, tangy lemon curd and smooth buttercream in perfect harmony.

# Ingredients:

→ Shortbread Crust

01 - 3 cups shortbread cookie powder (11-15oz pulsed into a powder)
02 - 5 tablespoons unsalted butter, melted
03 - 1 pinch salt

→ Lemon Cake

04 - 1 tablespoon fresh lemon zest (about 1 lemon)
05 - 3/4 cup buttermilk, room temperature
06 - 2/3 cup sour cream, room temperature
07 - 3 whole eggs, room temperature
08 - 1 egg white, room temperature
09 - 1 tablespoon vanilla extract
10 - 1 teaspoon lemon extract (optional)
11 - 1/3 cup vegetable oil
12 - 1/4 cup all-purpose flour
13 - 1 box (15.25oz) lemon cake mix (Duncan Hines preferred)

→ Lemon Curd

14 - 3 egg yolks
15 - 1 whole egg
16 - 3/4 cup granulated sugar
17 - 1/2 cup lemon juice
18 - 2 tablespoons lemon zest (about 2 lemons)
19 - 4 tablespoons unsalted butter

→ Lemon Buttercream

20 - 1 1/2 cups unsalted butter, slightly softened
21 - 1 teaspoon lemon extract
22 - 1 tablespoon vanilla extract
23 - 1 pinch salt
24 - 1/4 cup heavy cream
25 - 6-7 cups powdered sugar
26 - 1 drop yellow gel food coloring

→ Topping

27 - 1 cup shortbread cookies, crumbled

# Instructions:

01 - Prepare a 9x13 sheet pan with a light coating of shortening and a dusting of flour to prevent sticking. Preheat the oven to 325°F (165°C).
02 - Pulse shortbread cookies into a fine powder, then measure out 3 cups into a bowl. Add melted butter and salt, stirring until all butter is incorporated into the cookie powder. Press the mixture firmly into the prepared pan, using the bottom of a glass or measuring cup to create an even layer.
03 - In a large bowl, hand-whisk together lemon zest, buttermilk, sour cream, eggs, egg white, vanilla, lemon extract (if using), vegetable oil, and flour. Sift in the cake mix and gently stir until just incorporated.
04 - Pour the batter directly onto the unbaked shortbread crust. Bake for 28-30 minutes until a toothpick inserted in the center comes out clean. Allow to cool completely in the pan before decorating.
05 - While the cake bakes, combine egg yolks, whole egg, sugar, lemon juice, and zest in a medium saucepan over medium heat. Whisk continuously as the mixture thickens, about 6 minutes, until it coats the back of a spoon. Remove from heat and stir in butter cubes until melted. Strain to remove zest pieces. Cover with plastic wrap placed directly on the surface and refrigerate until completely cooled.
06 - In a stand mixer with paddle attachment, whip butter for about 1 minute until light and fluffy. Add salt, extracts, and heavy cream, mixing until combined. Gradually add powdered sugar, about 1/2 cup at a time. Mix in yellow gel coloring. Increase speed to high for 1 minute for aeration, then reduce to low for 30 seconds to remove air bubbles.
07 - Spread most of the buttercream in an even layer over the cooled cake. Reserve about 1 1/2 cups of buttercream in a piping bag fitted with a 1M tip. Pipe decorative lines of buttercream shells in a linear pattern. Fill the spaces between piped buttercream with the chilled lemon curd.
08 - Sprinkle crumbled shortbread cookies over the top of the cake for texture and added shortbread flavor.

# Notes:

01 - This cake combines the flavors of classic lemon bars with the texture of a sheet cake
02 - The cake can be stored covered in the refrigerator for up to 3 days
03 - For best flavor, allow cake to come to room temperature before serving

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